Sharif Ahmed
International Rice Research Institute, Bangladesh Office
Akbar Hossain
Bangladesh Wheat and Maize Research Institute, Nashipur, Dinajpur-5200, Bangladesh
Abu Abdullah Miajy
Rice Research Institute, Kala Shah Kaku, Punjab, Pakistan
Tahir H. Awan
Rice Research Institute, Kala Shah Kaku, Punjab, Pakistan
Pendimethalin, Pre-emergence, Herbicide, Soil moisture, Phytotoxicity, Phytotoxicity, Rice
Regional Agricultural Research Station (RARS) of Bangladesh Agricultural Research Institute (BARI), Jessore
Crop-Soil-Water Management
Weed management, Herbicide, Rice
The field experiment was conducted at the research farm of the Regional Agricultural Research Station (RARS) of Bangladesh Agricultural Research Institute (BARI), Jessore (23°11' N, 89°14' E and 16 m above mean sea level) in the boro (dry) season of 2012-13. The area belongs to the AEZ-11, of High Ganges River Floodplain. The climate of the area is subtropical, with an average annual rainfall of 1590 mm (90% of which is received during May to September), minimum temperature of 6–9 0C in January, and maximum temperature of 36– 440 C in April and May. The soil at 0–15-cm depth was a clay loam, with a bulk density of 1.56 Mg m3, a pH of 7.8, organic carbon of 1%, sand of 32%, silt of 31%, and clay of 37%. There experiment was arranged in a split-plot design with three replications. Main plots were assigned with time of herbicides application: (i) before sowing (BS) - herbicide was applied after land leveling and one day before sowing; (ii) after sowing but before irrigation (ASBI) (irrigation was applied shortly after sowing, on the same day); (iii) after sowing and irrigation (ASI) - herbicide was applied two days after irrigation; where sub-plots were arranged with weeding regimes (i) weed-free; (ii) partial weedy; (iii) oxadiargyl 80 g active ingredient (ai) ha-1 (iv) pendimethalin 1000 g ai ha-1. Size of the sub-plot size was 13.5 m2 (4.5 m x 3 m). All herbicides were applied using a knapsack-sprayer with a 1.2 m boom with three flat fan nozzles and spray volume was 450 L ha -1. To prevent the movement of herbicide after irrigation, the plots were separated by bunds and irrigated one plot at a time. In the weed-free treatment, weeds were removed by manual-hand weeding (at 10, 25, 35, 50 and 65 DAS) in five times. In the partial-weedy treatment, one hand weeding was performed at 40 DAS and weeds were allowed to grow before and after the hand weeding. One weeding was applied as in the absence of any weed control; there may be no or very little yield of DSR (Chauhan and Johnson, 2011). In addition, it is rare that farmers leave their rice fields infested with weeds throughout the season in irrigated areas. Dry seed of the rice var. BRRI dhan28 (life span 140 days) was sown on 1 February 2013 at 40 kg seed ha-1 and a row spacing of 20 cm. The crop was sown into dry tilled soil using a seed-drill with a fluted roller seed-metering device and a power tiller linked to a 2-wheel tractor. Fertilizer was applied at 160-20- 60-12-2.2 kg ha-1 of N-P-K-S-Zn, respectively (BRRI, 2011), in the forms of urea, triple superphosphate (TSP), MoP, gypsum, and zinc sulphate, respectively. Except for urea, other fertilizers were broadcast during final land preparation (prior to sowing). The urea was applied in four equal splits: at 14 DAS, tillering initiation stage (35 DAS), maximum tillering (55 DAS), and panicle initiation stage (65 DAS). A light irrigation was done just after sowing and the field was kept saturated up to 20 DAS and then irrigation were given based on soil water tension using a threshold value of 15 k Pa at 15 cm soil depth. At each irrigation, water was added until the depth of water on the soil surface reached 5 cm. Data on the density of rice plant (no. m-2) was determined at 14 DAS by counting the number of plants in 1 m of row length in five randomly selected locations in each plot. Weed density was determined at 20 DAS, and weed density and weed biomass were determined at 40 DAS and at anthesis; separated into grasses, broad leaf,and sedges. Total weeds biomass was also determined at the time of rice harvest. At each sampling time, all weeds were collected from two randomly located quadrats of 40 cm ×X 40 cm. The biomass was measured after oven drying the samples at 70 0C for 72 h. At harvest, panicle density (no. m-2) was determined by counting the number of panicles in 1 m row lengths at 4 randomly selected spots in each plot. Rice grain yield was determined from an area of 6.6 m2. Grain yield was converted to t ha− 1 at 14% moisture content. Regression analysis between weed biomass and rice grain yield was done using software Sigma Plot11.0 (Systat Software, Inc., Point Richmond, CA). All crop and weed data were analyzed ANOVA to evaluate differences between treatments and the means were separated using the least significant differences (LSD) at the 5% level of significance using statistical software Crop Stat 7.2.
Bangladesh Agron. J. 2019, 22(1): 15-25
Journal